The present invention relates to ribbon cable and a method of manufacturing the same.
At present, ribbon cable is typically produced by setting wires into a molten or partially molten resin and extruding the resultant combination as the resin cools. FIG. 1 shows a greatly expanded cross-sectional view of a prior art ribbon cable 2 constructed according to this method. A set of wires 4 are set into a resin coating 6. Note the misalignment of the wires 4, with some pairs of wires 4 being closer together than others and some wires 4 being at a different vertical level. This manufacturing procedure is perfectly adequate for most of the purposes for which ribbon cable is used. There are some applications, however, for which the availability of ribbon cable having more precisely positioned wires would be greatly beneficial.
In some biomedical equipment applications it is necessary to connect each wire of a ribbon cable to a contact pad on a flex circuit. If the wires of the ribbon cable are not precisely aligned, at least one of them might not be able to contact its corresponding contact pad. Currently, manufacturers know how to produce precisely aligned extruded ribbon cables having a dielectric coating of thermoplastic fluoropolymer, tetrafluoroethylene (“TFE,” most commonly marketed under the TEFLON® trademark) being the most well known. Thermoplastic fluoropolymers tend to be relatively hard materials that are difficult to remove using an ND:YAG laser (typically for the purpose of stripping the wires) than are some other dielectric materials such as polyurethane or polyimide. Moreover, the production of extruded, precisely aligned fluoropolymer ribbon cable requires precise adjustments, resulting in an expensive end product. Unfortunately, when a similar extrusion technique is used with polyurethane or polyimide, the product curls up as it comes out of the extruder. Accordingly, it is desirable to broaden the range of dielectric coatings that can be used to produce ribbon cables beyond those that can be made into an extrudable solution, plasma coating or powder coating.
It is also desirable to have accurately and uniformly positioned wires in a ribbon cable for the case in which a stack of ribbon cables must be threaded through a fixed size aperture. This situation occurs in the biomedical field in which tolerances for the transmission of signals within a particular spacing can be very tight. If the wires extend in a straight line in each cable, the cables may be stacked in a more compact form, with the ridges of a first ribbon cable fitting into the valleys of a second ribbon cable.